Thomas J McDonald

Roadway Lighting Shows Safety Benefits at Rural Intersections

Intersection-related crashes account for approximately 31% of fatal crashes in Minnesota and roughly 37% of those occurred at night, dusk, or dawn. Nationally, intersection-related fatal crashes accounted for 21% of all fatal crashes and 40% of those crashes occurred during dark, dusk, or dawn light conditions while only 25–33% of the vehicle miles traveled occur at night. Furthermore, Minnesota experienced 70% of its fatal crashes in rural areas, as compared to 58% nationally. As a result, rural intersections at night are at higher risk for fatal crashes than other locations in Minnesota. This research was part of Research Rep. No. MN/RC-2006-35, “Safety impacts of street lighting at isolated rural intersections—Part II.” This research evaluated the effectiveness of roadway lighting in reducing nighttime crashes at isolated rural intersections. A before-and-after study was used to evaluate the impact of lighting at 33 intersections with 3 years of before data and 3 years of after data. A Poisson regressi...

Investigation of Violation Reduction at Intersection Approaches with Automated Red Light Running Enforcement Cameras in Clive, Iowa, Using a Cross-Sectional Analysis

Red light running causes more than 100,000 crashes and 1,000 fatalities annually and results in an estimated economic loss of over

Assessing the Safety Impacts of Paved Shoulders

14 billion per year in the United States. Red light running is a significant safety issue facing communities which rarely have the resources to place additional law enforcement in the field. As a result, communities are increasingly turning to automated red light running camera-enforcement systems to address the problem. The effectiveness of red light running cameras in reducing the number of drivers who run the red light (violations) in an Iowa community was evaluated. The number of red light running violations at camera-enforced intersection approaches were compared to violations at approaches at intersections where cameras were not used within the same metropolitan area using a cross-sectional analysis. A Poisson lognormal regression was used to evaluate the effectiveness of the cameras in reducing violations. Results indicated that red light running cameras substantially reduced the number of violations at camera-enforced approaches as compared to control approaches.

Safety Effectiveness of Stop Control at Ultralow-Volume Unpaved Intersections

Single-vehicle run-off-road crashes in Iowa account for 36% of all rural crashes and 62% of rural fatal crashes. Paved shoulders are a potential countermeasure for run-off-road crashes, and several studies have indicated that paved shoulders are effective in reducing crashes. However, the number of studies that quantify the benefits is limited. This article summarizes a before-and-after study to evaluate the impact of paved shoulders on crashes in Iowa to provide additional information for the Iowa Department of Transportation who had adopted a paved shoulder policy for higher volume roads. Bayesian inference for negative binomial-Lindley generalized linear models were developed to assess this relationship. Results suggested a relationship between total crashes and total right shoulder width, presence of a median, speed limit, presence of paved shoulders, season, and year-after intervention. The model for run-off-road crashes indicated a relationship with total right shoulder width, presence of a median, speed limit, presence of paved shoulders, season, and year after intervention. The model for single-vehicle run-off-road crashes indicated a relationship with total width of right shoulder, presence of a median, speed limit, presence of paved shoulders, season, and year-after intervention.

Field application and assessment of the safety edge

Establishment of the proper level of traffic control on low-volume rural roads can be problematic for local agencies. Ten years of crash data for more than 6,000 rural, unpaved intersections in Iowa were analyzed, with stop-controlled intersections compared with uncontrolled intersections. Crash models were developed with logistic regression and hierarchical Poisson estimation. For ultralow-volume intersections, those used by fewer than 150 vehicles per day, results indicated no statistical difference in the safety performance of each level of control. The effect of excessive use of control on safety performance also was tested for rural and urban applications, with no detrimental effect generally being indicated.

EFFECTIVENESS OF ALL-RED CLEARANCE INTERVAL ON INTERSECTION CRASHES

Pavement edge drop-off can be a serious safety concern when a vehicle leaves the paved roadway surface and encounters a significant difference in vertical elevation between the paved roadway and the adjacent unpaved shoulder. Edge drop-offs are potential safety hazards because scrubbing between the pavement edge and tire can result in loss of control. FHWA developed the Safety Edge on the basis of research results that indicated a sloped pavement edge surface could be more easily traversed by a vehicle leaving its lane and attempting to remount the pavement edge. The Safety Edge is a design feature that creates an approximate 30° fillet along the outside edge of the paved section of a roadway. Although a number of benefits have been attributed to the Safety Edge, agencies in Iowa were slow to adopt it. To accelerate use of the Safety Edge, the research team marketed and monitored it in Iowa during the 2010 construction season. This project provided the opportunity to evaluate the Safety Edge as well as summarize lessons learned from agencies and contractors. Evaluation of the Safety Edge included assessment of the consistency of slope application, identification of common problems during construction, measurement of the density of the Safety Edge, and computation of the approximate additional material needed to construct the Safety Edge. The team also measured drop-off formation along previously constructed Safety Edge sites and compared this with control sites to assess any difference in occurrence.